The study of hypertrophy isolated muscle preparations requires the maintenance of preparations for long periods of time (48 hours) and could consume large quantities of radioactive material. A unique organ culture apparatus for papillary muscle preparations was developed to protect the muscle from infection, prevent the release of contaminants to the environment, and minimize the amount of radioactive material required. The apparatus contains an isometric myograph for detailed physiological studies. The preparations have been shown to remain viable based on physiological parameters (developed tension, and response to chemical changes). Data have shown that a protein which undergoes phosphorylation in the system has the same molecular weight as a subunit of myosin. The degree of phosphorylation is greatly enhanced (approximately 2.5 times) in those muscles treated with norepinephrine for approximately 5 minutes compared to untreated controls running simultaneously. It is felt that the apparatus will enable detailed study of phosphorylation of muscle and its possible role in contractility. With minor modification the equipment could be applied to a variety of tissue preparations, particularly embryological systems.